Some ink-jet printers, such as manufactured by Hewlett-Packard Company under the designation DeskJet, include a cartridge or "pen" that is mounted to a carriage in the printer. The pen includes a body that defines a reservoir of ink, and a print head that is operated for ejecting minute ink drops onto paper that is advanced through the printer.
Prior ink-jet pens have been constructed so that the print head is irremovably attached to the pen body, thereby preventing replacement of a print head without damage to the pen.
Some ink-jet printer pens can be designed to include more than one print head. For example, a pen can be constructed to include a plurality of print heads that span across the entire width of a page that is advanced through the printer.
In the event that such a multiple-print-head pen were manufactured using conventional techniques, the entire pen would have to be assembled before the printing characteristics of the print heads could be tested. A failure of one of the print heads, therefore, would ruin the entire pen and lead to expensive waste or re-work for repairing the pen.
The present invention is directed to a construction whereby ink-jet printer pens have modular or unit print head assemblies that can be readily mounted to and removed from a pen body in the event that the assembly needs repair or replacement. Moreover, the print heads of an individual unit print head assembly may be fully tested before that assembly is joined with several other parts in manufacturing a pen.